1. Field of the Invention
The present invention relates to a polyorganosiloxane with a carboxyl group at one terminal position, and to a method for producing it. Precisely, the invention relates to a modified carboxyl-terminated polyorganosiloxane which has a polyoxyalkylene segment between the carboxyl group at one terminal position and the polyorganosiloxane segment, and to a method for producing it.
2. Description of the Related Art
As having good weather resistance, surface water repellency, surface smoothness and lubricity, polyorganosiloxanes have many applications as modifiers for various polymers. For modifying polymer fibers, for example, employed are (1) a method of applying a polyorganosiloxane emulsion onto the fiber surface to improve the surface smoothness of the fibers; and (2) a method of kneading a polyorganosiloxane with a polymer such as polyester or the like followed by forming the resulting blend into fibers, to thereby modify the surface characteristics of the fibers.
In the method of applying a polyorganosiloxane onto the fiber surface, however, it is known that the polyorganosiloxane often peels off from the fiber surface owing to the friction between the fibers inevitable therein, whereby the surface smoothness of the fibers is lowered. On the other hand, the method of kneading a polyorganosiloxane with a polymer such as polyester or the like is also problematic in that the polyester and the polyorganosiloxane are difficult to uniformly mix since their miscibility is poor, and that the polyorganosiloxane often bleeds out on the polymer fibers. In the two methods, therefore, the surface smoothness of the fibers could be improved only temporarily.
Of polyorganosiloxanes, those having a functional group are effective as modifiers for various polymers. For example, such a polyorganosiloxane is used as a component for copolymerization or polycondensation with a polymer, to thereby make the resulting polymer have weather resistance, surface water repellency, lubricity, bio-compatibility and gas permeability characteristic of the organopolysiloxane used.
For modifying polymers, known are polyorganosiloxanes having various organic functional groups. For example, polyorganosiloxanes having a carboxyl group, such as those modified by carboxyl group at one terminal position, are useful as fiber-processing agents, emulsifiers, surface modifiers for inorganic materials, and also modifiers for various resins such as epoxy resins, polyesters, alkyd resins, urethane resins, etc.
Utilizing the reactivity of the carboxyl group therein, various additional functional groups may be introduced into the modified polyorganosiloxanes to produce different polyorganosiloxanes having various functional groups. For example, the carboxyl group may be amidated or esterified. In that manner, polyorganosiloxanes modified by carboxyl group at one terminal position can be utilized for preparing various types of modified silicones.
Japanese Patent Laid-Open No. 001537/1998 discloses modification of polyesters with polyorganosiloxanes that are modified by carboxylation at both terminal position; and Japanese Patent Publication No. 068424/1995 discloses a technique of using a carboxyl group-containing polyorganosiloxane for improving the cold resistance of an acrylic rubber composition and a technique of using the acrylic rubber composition for improving the mold releasability and the roll workability of acrylic rubber.
Japanese Patent Laid-Open No. 059125/1997 discloses a technique of coating the surface of a powder for cosmetics with a carboxyl group-containing polyorganosiloxane to thereby make the powder repel water.
Japanese Patent Laid-Open No. 109263/1996 discloses a technique of converting a polyorganosiloxane modified by carboxylation at both terminal position and side chain carboxylation into a polyvalent metal salt-modified polyorganosiloxane, and using it as a gelling agent or for cosmetics.
Japanese Patent Laid-Open No. 139997/1993 discloses a technique of using a carboxyl group-containing polyorganosiloxane for an endermic absorption promoter.
Such useful modified polyorganosiloxanes with a carboxyl group at one terminal position, can be produced in various methods mentioned below. For example, one method for producing them comprises adding an unsaturated carboxylate to a polydimethylsiloxane with an SiH group at one terminal position, through hydrosilylation in the presence of a platinum catalyst, followed by hydrolyzing the ester group in the resulting adduct into a carboxyl group; and another method comprises adding a silyl ester of an unsaturated carboxylic acid to a polydimethylsiloxane with an SiH group at one terminal position, through hydrosilylation in the presence of a platinum catalyst, followed by processing the resulting adduct with water or an alcohol to remove the silyl group from it to thereby make it have a carboxyl group.
As mentioned hereinabove, the usefulness of carboxyl-modified polyorganosiloxanes is obvious.
However, the conventional methods require three reaction steps including a step of protecting the carboxyl group with a silyl group prior to hydrosilylation, since the carboxyl group interferes with the hydrosilylation. Accordingly, it is desired to produce modified polyorganosiloxanes with a carboxyl group at one terminal position in one-step reaction. In addition, the conventional, carboxyl group-containing polyorganosiloxanes are problematic in that their miscibility with various solvents is low, and their applications are limited.
The present invention is to solve the prior art problems noted above, and its object is to provide a polyorganosiloxane with a carboxyl group at one terminal position, having a polyoxyalkylene moiety in the center of its molecular chain, and to provide a method for producing it in one-step reaction.
We, the present inventors have assiduously studied so as to solve the above-mentioned prior art problems. As a result, we have found that a polyorganosiloxane with a carboxyl group at one terminal position and having a polyoxyalkylene moiety in the center of its molecular chain is highly miscible with various polar solvents and monomers. In addition, we have found a novel method for producing the modified polyorganosiloxane, which comprises reacting a polyorganosiloxane with a hydroxyl group at one terminal position and having a polyoxyalkylene moiety in the center of its molecular chain, with a cyclic acid anhydride having a specific structure. The method does not require plural reaction steps, and according to the method, it is easy to produce different types of carboxyl-terminated polyorganosiloxanes at one terminal position in different modes depending on the type of the starting cyclic acid anhydride used. On the basis of these findings, we have completed the present invention.
1. A modified carboxyl-terminated polyorganosiloxane having a mean molecular weight of from 500 to 120,000 and represented by the following general formula (1): 
wherein R1, R2, R3, R4, and R5 each represent a linear or branched alkyl group having from 1 to 20 carbon atoms, an aryl-containing group having from 6 to 10 carbon atoms, or a cycloalkyl group having from 4 to 10 carbon atoms; n and m each represent a number of 0, 1 or more; n+m indicates a number to satisfy the mean molecular weight, from 500 to 100,000, of the polysiloxane segment; X represents an alkylene group having from 2 to 20 carbon atoms; Y represents an oxyalkylene group having from 1 to 3 carbon atoms; p represents a number to satisfy the mean molecular weight, from 30 to 20,000, of the polyoxyalkylene segment Yp; and A represents a substituent having from 1 to 6 carboxyl groups.
2. The modified carboxyl-terminated polyorganosiloxane of above item 1, wherein p is a number to satisfy the mean molecular weight, from 120 to 20,000, of the polyoxylalkylene segment Yp.
3. The modified carboxyl-terminated polyorganosiloxane of above item 1, wherein A is a substituent Z having from 1 to 3 carboxyl groups.
4. The modified carboxyl-terminated polyorganosiloxane of above item 1, wherein A is a substituent of the following general formula (2): 
wherein R6 represents a hydrogen atom, a linear or branched alkyl group having from 1 to 5 carbon atoms, or an aryl group having from 6 to 10 carbon atoms; and Z represents a substituent having from 1 to 3 carboxyl groups.
5. The modified carboxyl-terminated polyorganosiloxane of above items 3 or 4, wherein Z is a substituent of the following general formula (3): 
wherein R7 represents a polyvalent alkyl-, alkenyl, aryl, or arylalkyl radical that may optionally contain functional groups selected from carbonyl groups, sulfone groups, ethereal oxygen groups, amine groups, and trifluoromethyl groups; and R8 and R9 each represent a hydrogen atom or a carboxyl group.
6. The modified carboxyl-terminated polyorganosiloxane of above items 3 or 4, wherein Z is a substituent of the following general formula (4): 
wherein R7 represents a polyvalent alkyl-, alkenyl, aryl, or arylalkyl radical that may optionally contain functional groups selected from carbonyl groups, sulfone groups, ethereal oxygen groups, amine groups, and trifluoromethyl groups.
7. The modified carboxyl-terminated polyorganosiloxane of above items 1 or 2, where Y is xe2x80x94OCH2xe2x80x94, xe2x80x94OCH(CH3)xe2x80x94, xe2x80x94OCH2CH2xe2x80x94, xe2x80x94OCH(CH3)CH2xe2x80x94, or xe2x80x94OCH2CH(CH3)xe2x80x94; and X is an alkylene group having from 2 to 5 carbon atoms.
The method of the invention for producing a modified carboxyl-terminated polyorganosiloxane includes the following items 8 to 14:
8. A method for producing a modified carboxyl-terminated polyorganosiloxane of the following general formula (1), which comprises reacting a silicone with a hydroxyl group at one terminal position and represented by the following general formula (5), with at least one acid anhydride selected from the group of the compounds of the following general formulae (6), (7) and (8), in the presence of a catalyst: 
wherein R1, R2, R3, R4, and R5, each represent a linear or branched alkyl group having from 1 to 20 carbon atoms, an aryl-containing group having from 6 to 10 carbon atoms, or a cycloalkyl group having from 4 to 10 carbon atoms; n and m each represent a number of 0, 1 or more; n+m indicates a number to satisfy the mean molecular weight, from 500 to 100,000, of the polysiloxane segment; X represents an alkylene group having from 2 to 20 carbon atoms; Y represents an oxyalkylene group having from 1 to 3 carbon atoms; p represents a number to satisfy the mean molecular weight, from 30 to 20,000, of the polyoxyalkylene segment Yp; and A represents a substituent having from 1 to 6 carboxyl groups, 
wherein R1, R2, R3, R4, and R5 each represent a linear or branched alkyl group having from 1 to 20 carbon atoms, an aryl-containing group having from 6 to 10 carbon atoms, or a dycloalkyl group having from 4 to 10 carbon atoms; n and m each represent a number of 0, 1 or more, n+m indicates a number to satisfy the mean molecular weight, from 500 to 100,000, of the polysiloxane segment; X represents an alkylene group having from 2 to 20 carbon atoms; Y represents an oxyalkylene group having from 1 to 3 carbon atoms; p represents a number to satisfy the mean molecular weight, from 30 to 20,000, of the polyoxyalkylene segment Yp; and B represents a substituent having one or two hydroxyl groups, 
wherein R7 represents a polyvalent alkyl-, alkenyl, aryl, or arylalkyl radical that may optionally contain functional groups selected from carbonyl groups, sulfone groups, ethereal oxygen groups, amine groups, and trifluoromethyl groups.
9. The method for producing a modified carboxyl-terminated polyorganosiloxane of above item 8, wherein p is a number to satisfy the mean molecular weight, from 120 to 20,000, of the polyoxyalkylene segment Yp.
10. The method for producing a modified carboxyl-terminated polyorganosiloxane of above item 8, wherein A is a substituent Z having from 1 to 3 carboxyl groups, and B is a hydroxyl group.
11. The method for producing a modified carboxyl-terminated polyorganosiloxane of above item 8, wherein A is a substituent of the following general formula (2), and B is a substituent of the following general formula (9): 
wherein R6 represents a hydrogen atom, a linear or branched alkyl group having from 1 to 5 carbon atoms, or an aryl group having from 6 to 10 carbon atoms; and Z represents a substituent having from 1 to 3 carboxyl groups, 
wherein R6 represents a hydrogen atom, a linear or branched alkyl group having from 1 to 5 carbon atoms, or an aryl group having from 6 to 10 carbon atoms.
12. The method for producing a carboxyl-terminated, modified polyorganosiloxane of above items 10 or 11, wherein Z is a substituent of the following general formula (3): 
wherein R7 represents a polyvalent alkyl-, alkenyl, aryl, or arylalkyl radical that may optionally contain functional groups selected from carbonyl groups, sulfone groups, ethereal oxygen groups, amine groups, and trifluoromethyl groups; and R8 and R9 each represent a hydrogen atom or a carboxyl group.
13. The method for producing a modified carboxyl-terminated polyorganosiloxane of above items 10 or 11, wherein Z is a substituent of the following general formula (4): 
wherein R7 represents a polyvalent alkyl-, alkenyl, aryl, or arylalkyl radical that may optionally contain functional groups selected from carbonyl groups, sulfone groups, ethereal oxyqen groups, amine groups, and trifluoromethyl groups.
14. The method for producing a modified carboxyl-terminated polyorganosiloxane of above item 8, wherein Y is xe2x80x94OCH2xe2x80x94, xe2x80x94OCH(CH3)xe2x80x94, xe2x80x94OCH2CH2xe2x80x94, xe2x80x94OCH(CH3)CH2xe2x80x94, or xe2x80x94OCH2CH(CH3)xe2x80x94; and X is an alkylene group having from 2 to 5 carbon atoms.